New release 5.5.2 of Therion

[Martin Sluka]

Hi, there is a new release 5.5.2 of Therion. https://therion.speleo.sk
Release notes (mostly about managing of large projects):

Therion 5.5.2 (2020-10-09):

therion:
* added extend ignore path -- extend ignore <station1> <station2> <station3>
* added ratio of extended elevation -- extend <0..100>
* support CMYK colors in MetaPost symbols (this is not yet a complete CMYK support)
* updated WKT definitions for some built-in projections
* the names of projections defined by EPSG/ESRI are loaded dynamically from the Proj database if Proj version >= 6
* undated surveys are listed in the Therion messages
* documentation updates
* updated German translation [#258]
* bugs fixed
- use proper ISO code for Czech language ('cs' instead of 'cz') [#251]; 'cz' is still allowed in the map layout for backwards compatibility
- pdftex included in the windows installer failed to find images with '/./' or '/../' in the file path
- splay shots extended elevation processing
- another fix for Proj 7.1.0 axes swap in Krovak's projection
- refuse to compile with unsupported Proj versions
- depth is incorrectly taken from surface legs
- Survex err reading bugfix
- VTK9 compatibility fixes
- Xtherion map georeferencing bugfix
- mingw-w64 compatibility fixes
- wxWidgets compilation issues
- declination set to 0 outside of the geomag model range (now the declination is extrapolated 15 years after the model date; error is produced after that and before 1900)
- other minor fixes

infrastructure:
* add more Travis CI targets, update the libraries used
* removed Therion library rebuilding